Khi quan sát quá trình phân bào của một tế bào sinh dưỡng ở một loài sinh vật có bộ nhiễm sắc thể lưỡng bội 2n, một học sinh vẽ lại được sơ đồ với đầy đủ các giai đoạn khác nhau như sau:   Cho các phát biểu sau đây: (1) Quá trình phân bào này mô tả cơ chế tạo thể lệch bội trong giảm phân. (2) Quá trình phân bào này có một cặp nhiễm sắc thể không phân li trong nguyên phân. (3) Bộ nhiễm sắc lưỡng bội của loài trên là 2n = 8. (4) Ở giai đoạn (f), tế bào có 8 phân tử ADN thuộc 4 cặp nhiễm sắc thể. (5) Thứ tự các giai đoạn xảy ra là: (b) → (d) → (f) → (e) → (a) + (c) Số phát biểu đúng là:  

Trên tiêu bản kỳ sau cùa nguyên phân của một tế bào một loài thực vật là thể một kép người ta đếm được 44 nhiễm sắc thể. Bộ nhiễm sắc thể lưỡng bội bình thường cùa loài này là:  

Giả sử có 3 tế bào vi khuẩn E.coli, mỗi tế bào có chứa một phân tử ADN vùng nhân được đánh dấu bằng N15 ở cả hai mạch đơn. Người ta nuôi các tế bào vi khuẩn này trong môi trường chỉ chứa N14 mà không chứa N15 trong thời gian 3 giờ. Trong thời gian nuôi cấy này thời gian thế hệ của vi khuẩn là 20 phút. Cho biết không xảy ra đột biến, có bao nhiêu dự đoán sau đây đúng?         

(1) Số phân tử ADN vùng nhân thu được sau 3 giờ là 1536.   

(2) Số mạch đơn ADN vùng nhân chứa N14 thu được sau 3 giờ là 1533.         

(3) Số phân tử ADN vùng nhân chứa N14 thu được sau 3 giờ là 1530.         

(4) Số mạch đơn ADN vùng nhân chứa N15 thu được sau 3 giờ là 6.  

Giả sử từ một tế bào vi khuẩn có 3 plasmit, qua 2 đợt phân đôi bình thường liên tiếp thu được các tế bào con. Theo lý thuyết, có bao nhiêu kết luận sau đây đúng?

(1) Quá trình phân bào của vi khuẩn này không có sự hình thành thoi phân bào.

(2) Vật chất di truyền trong tế bào vi khuẩn này luôn phân chia đồng đều cho các tế bào con.

(3) Có 4 tế bào vi khuẩn được tạo ra, mỗi tế bào luôn có 12 plasmit.

(4) Mỗi tế bào vi khuẩn được tạo ra có 1 phân tử ADN vùng nhân và không xác định được số plasmit.

(5) Trong mỗi tế bào vi khuẩn được tạo ra, luôn có 1 phân tử ADN vùng nhân và 1 plasmit.         

Một tế bào lưỡng bội bình thường nguyên phân, số NST trong tế bào ở kỳ giữa là bao nhiêu?        

Ở một loài thực vật, bộ NST lưỡng bội là 2n = 20. Quá trình nguyên phân liên tiếp 4 lần từ tế bào sinh dục sơ khai đã cần môi trường cung cấp nguyên liệu tương đương 285 NST. Tế bào sinh dục sơ khai có bộ NST như thế nào ?  

Trong nguyên phân những thể đa bội nào sau đây được tạo thành?

 Muốn tạo ra đột biến gen hiệu quả nhất thì tác động vào pha nào trong các pha sau:

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase thet best fits each of the numbered blanks from 24 to 28:

 Imagine you are studying English at a small college in the Midwestern United States. The local newspaper rarely has news about your native country. (24) _______, it prints very little foreign news, but this does not bother you at all. You sit comfortably in your apartment, turn on your (25) _______ computer, and ask for the foreign news. The screen is immediately (26) _______ with news from (27) _______ the world. Computers have (28) _______ an information “superhighway”. Today, computers can work together - they can network with each other. The worldwide computer network is called the Internet. Using the Internet, you can find all kinds of information and news from people and countries around the world.

Question 25:       

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase thet best fits each of the numbered blanks from 24 to 28:

 Imagine you are studying English at a small college in the Midwestern United States. The local newspaper rarely has news about your native country. (24) _______, it prints very little foreign news, but this does not bother you at all. You sit comfortably in your apartment, turn on your (25) _______ computer, and ask for the foreign news. The screen is immediately (26) _______ with news from (27) _______ the world. Computers have (28) _______ an information “superhighway”. Today, computers can work together - they can network with each other. The worldwide computer network is called the Internet. Using the Internet, you can find all kinds of information and news from people and countries around the world.

Question 27:        

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase thet best fits each of the numbered blanks from 24 to 28:

 Imagine you are studying English at a small college in the Midwestern United States. The local newspaper rarely has news about your native country. (24) _______, it prints very little foreign news, but this does not bother you at all. You sit comfortably in your apartment, turn on your (25) _______ computer, and ask for the foreign news. The screen is immediately (26) _______ with news from (27) _______ the world. Computers have (28) _______ an information “superhighway”. Today, computers can work together - they can network with each other. The worldwide computer network is called the Internet. Using the Internet, you can find all kinds of information and news from people and countries around the world.

Question 28:        

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase thet best fits each of the numbered blanks from 31 to 35:

 In the western customs (31) _____ hands is the customary form of greeting, but in China a nod of the head or (32) ____ bow is sufficient. Hugging and kissing when greeting are uncommon. Business cards are often (33) _____ and yours should be printed in your own language and in Chinese. Also, it is more respectful to present your card or a gift or-any other article using (34) _____ hands. The Chinese are (35) _____ applauders. You may be greeted with group clapping, even by small children. When a person is applauded is this practice it is the custom for that person to return the applause or a “thank you”.   

Question 31:

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase thet best fits each of the numbered blanks from 31 to 35:

 In the western customs (31) _____ hands is the customary form of greeting, but in China a nod of the head or (32) ____ bow is sufficient. Hugging and kissing when greeting are uncommon. Business cards are often (33) _____ and yours should be printed in your own language and in Chinese. Also, it is more respectful to present your card or a gift or-any other article using (34) _____ hands. The Chinese are (35) _____ applauders. You may be greeted with group clapping, even by small children. When a person is applauded is this practice it is the custom for that person to return the applause or a “thank you”.   

Question 32:

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase thet best fits each of the numbered blanks from 24 to 28:

 Although it may come as a surprise to many people, postal services have existed in some parts of the world for thousands of years. There is ample evidence that a postal services existed among the Assyrians and Babylonians. In China a regular postal service was established in the seventh century BC, and over the centuries attained such a high level of efficiency that some 2000 years after its (24) _______ it won the admiration of travelers like Marco Polo. Efficient and highly developed postal services were also established in the Persia and Roman Empires. In ancient times, these services were mainly confined to the use of representative of the state; private citizens made use of slaves, merchants and the (25) _______ to send their messages and documents. In Medieval Europe, postal services were organized by emperors and by the papacy, (26) _______ private citizens continued to entrust their correspondence to various travelers. Later around the 13th century, universities and towns came to have the own messengers. However, it was not until the 14th century when merchants, the private citizens who had the greatest need for a speedy and regular exchange of correspondence, began to set (27) _______ regular courier services. The needs of business (28) _______ to the development of the postal services as we know it today.

Question 24:

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase thet best fits each of the numbered blanks from 24 to 28:

 Although it may come as a surprise to many people, postal services have existed in some parts of the world for thousands of years. There is ample evidence that a postal services existed among the Assyrians and Babylonians. In China a regular postal service was established in the seventh century BC, and over the centuries attained such a high level of efficiency that some 2000 years after its (24) _______ it won the admiration of travelers like Marco Polo. Efficient and highly developed postal services were also established in the Persia and Roman Empires. In ancient times, these services were mainly confined to the use of representative of the state; private citizens made use of slaves, merchants and the (25) _______ to send their messages and documents. In Medieval Europe, postal services were organized by emperors and by the papacy, (26) _______ private citizens continued to entrust their correspondence to various travelers. Later around the 13th century, universities and towns came to have the own messengers. However, it was not until the 14th century when merchants, the private citizens who had the greatest need for a speedy and regular exchange of correspondence, began to set (27) _______ regular courier services. The needs of business (28) _______ to the development of the postal services as we know it today.

Question 26:

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase thet best fits each of the numbered blanks from 24 to 28:

 Although it may come as a surprise to many people, postal services have existed in some parts of the world for thousands of years. There is ample evidence that a postal services existed among the Assyrians and Babylonians. In China a regular postal service was established in the seventh century BC, and over the centuries attained such a high level of efficiency that some 2000 years after its (24) _______ it won the admiration of travelers like Marco Polo. Efficient and highly developed postal services were also established in the Persia and Roman Empires. In ancient times, these services were mainly confined to the use of representative of the state; private citizens made use of slaves, merchants and the (25) _______ to send their messages and documents. In Medieval Europe, postal services were organized by emperors and by the papacy, (26) _______ private citizens continued to entrust their correspondence to various travelers. Later around the 13th century, universities and towns came to have the own messengers. However, it was not until the 14th century when merchants, the private citizens who had the greatest need for a speedy and regular exchange of correspondence, began to set (27) _______ regular courier services. The needs of business (28) _______ to the development of the postal services as we know it today.

Question 25: 

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase thet best fits each of the numbered blanks from 24 to 28:

 Although it may come as a surprise to many people, postal services have existed in some parts of the world for thousands of years. There is ample evidence that a postal services existed among the Assyrians and Babylonians. In China a regular postal service was established in the seventh century BC, and over the centuries attained such a high level of efficiency that some 2000 years after its (24) _______ it won the admiration of travelers like Marco Polo. Efficient and highly developed postal services were also established in the Persia and Roman Empires. In ancient times, these services were mainly confined to the use of representative of the state; private citizens made use of slaves, merchants and the (25) _______ to send their messages and documents. In Medieval Europe, postal services were organized by emperors and by the papacy, (26) _______ private citizens continued to entrust their correspondence to various travelers. Later around the 13th century, universities and towns came to have the own messengers. However, it was not until the 14th century when merchants, the private citizens who had the greatest need for a speedy and regular exchange of correspondence, began to set (27) _______ regular courier services. The needs of business (28) _______ to the development of the postal services as we know it today.

Question 28:

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase thet best fits each of the numbered blanks from 24 to 28:

 Although it may come as a surprise to many people, postal services have existed in some parts of the world for thousands of years. There is ample evidence that a postal services existed among the Assyrians and Babylonians. In China a regular postal service was established in the seventh century BC, and over the centuries attained such a high level of efficiency that some 2000 years after its (24) _______ it won the admiration of travelers like Marco Polo. Efficient and highly developed postal services were also established in the Persia and Roman Empires. In ancient times, these services were mainly confined to the use of representative of the state; private citizens made use of slaves, merchants and the (25) _______ to send their messages and documents. In Medieval Europe, postal services were organized by emperors and by the papacy, (26) _______ private citizens continued to entrust their correspondence to various travelers. Later around the 13th century, universities and towns came to have the own messengers. However, it was not until the 14th century when merchants, the private citizens who had the greatest need for a speedy and regular exchange of correspondence, began to set (27) _______ regular courier services. The needs of business (28) _______ to the development of the postal services as we know it today.

Question 27: